383. Ransom Note
Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false.
Each letter in the magazine string can only be used once in your ransom note.
Note: You may assume that both strings contain only lowercase letters.
canConstruct("a", "b") -> false canConstruct("aa", "ab") -> false canConstruct("aa", "aab") -> true简单map
class Solution { public: bool canConstruct(string ransomNote, string magazine) { map<char, int> mp; for (int i = 0; i< magazine.size(); i++) { mp[magazine[i]] ++; } for (int i = 0; i< ransomNote.size(); i++) { if (mp.find(ransomNote[i]) == mp.end()) return false; else if ( --mp[ransomNote[i]] == 0) mp.erase(ransomNote[i]); } return true; } };
